Air cycle cooling unit



NGV' 5, 1963 J. J. DINEEN 3,109,583

AIR CYCLE COOLING UNIT Filed DeC. s. 1960 s sheets-sheet I INTAKE COLD AIR TO CAE Tir-19.2

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TTOR EYS J. J. DINEEN 3,109,583

Nov. 5, 1963 AIR CYCLE COOLING UNIT Filed Dec. 8. 1960 3 Sheets-Sheet 2 l wiss-ron I INLET-ro spmenoN-q bawue-r FRoM M w. ExPANswN CHAMBERS B /1 y2/,m14 'r @NW ArroRNEvs Nov. 5, 1.963 J. J. DINEEN AIR CYCLE COOLING UNIT 3 Sheets-Sheet 3 Filed Dec. 8. 1960 INLET STROKE OMPRESSI N STROKE .11AM a T. .ml

ATTORNEYS United States Patent C)v 3,169,583 AER CYCLE COOLING UNH' .lohn J. Dine-en, East Northport, NY., assigner to Chandler Evans Corporation, West Hartford, Conn., a `cerperatitm cf Sonrreeticut Filed Dec. 8, 1961i, Ser. No. 74,634) Claims. (Cl. 23d-196) This invention relates to an air cycle cooling unit, and particularly such a unit designed for cooling the air in an enclosed space such as the cab of a truck or the interior of a bus or other motor vehicle. This application is a continuation-in-part of co-pending application Ser. No. 839,418 filed September l1, 1959 now Patent No. 2,997,862.

It is an object of the invention to provide such a cooling unit of improved eiciency and compactness, with an expansion cylinder inside the compression cylinder, the compression piston serving as the expansion cylinder, with a combined piston ring and inlet valve, and with other mechanical improvements.

lIt is a further object to provide a cooling unit in which the air to be cooled is compressed, passed through an aircooled heat exchanger, expanded, and supplied as relatively cold air to the interior of the truck cab or other space.

It is another object to provide a cooling unit in which the outside air is drawn through the heat exchanger along a path generally counter to the flow of the compressed air to be cooled, and passes yalso in heat-exchange relation to the wall of the compressor.

yIt is also an object to provide a seal ring or disc associated with the compressor piston to permit the free passage of air into the compression chamber on the intake stroke of the piston and to prevent the escape of air from said chamber on the compression stroke.

lIt is a further object to provide certain improvements in the form, construction, arrangement and materials of the several parts whereby the above named and other objects may effectively be attained.

A practical embodiment of the invention is shown in the accompanying drawings, wherein:

FIG. `1 represents a vertical axial section through a complete one-cylinder unit in the plane of the drive shaft, parts of the heat exchanger cowling being shown in elevation and parts being broken away, the compressor piston being shown at the bottom of its stroke;

tF-IG. 2 represents a section as in FIG. l, omitting part of the heat exchanger and showing the compressor piston substantially at the top of its stroke;

FIG. 3 represents a transverse vertical section on the line lIILJIII of FIG. 1;

FIG. 4 represents a detail horizontal sectional view of the combined piston ring and inlet valve, taken on the line lVMiV of FIG. 3;

iFlG. 5 represents, somewhat diagrammatically, a transverse cross-sectional view of a plural-Cylinder unit;

FIG. 6 represents a detail top plan view of a rnodied form of valve, and

FIG. 7 represents an axial section through the valve of FIG. 6 and the correspondingly modified piston, taken on the `line Vil- VH of FIG. 5.

Referring to the drawings, the unit is shown as comprising a compnession block 1 having a cylindrical compression chamber 2, spaced lower crank-case portions 3, 4, and a valve block 45 within the upper cylindrical crankcase portion 5. rl'he drive shaft 6 is journaled at 7, 8 in the outer walls of the portions 3, 4, `5 and passes through a horizontal bore 6 in the block S. The compressor piston 9 has a Adownwardly projecting inwardly cylindrical part '10 which constitutes the lateral wall of an expansion chamber -11, the top and bottom walls of which are con- ICC bad stituted by the under surface of piston 9 and the upper surface of valve block 5. A suitable seal 12 is provided adjacent the upper periphery of block 5 and designed to bear against the inner cylindrical surface of the part 1G'.

At diametrically opposite points on the outside of the part :lll are mounted the studs 13, alined fwith eccentrics 14 on the drive shaft, and connecting rods 15 embrace said eccentrics and connect them to the studs 113, with the provision of suitable `anti-friction bearings between the connecting rods and the eccentrics and studs.

The valve block is provided with four vertical bores, the bores 16 and 1'7 extending downward from the top of the block to the horizontal bore 6' and having their axes in the same vertical plane with the axis of the drive shaft 6, and the bores 1S, 19 extending upward from the bottom of the block toward, but not to, the upper surface thereof, said latter bores being so located in the block that they do not intersect any of bores 6', 16 and 17; certain connections being provided, however, as described below.

The upper periphery of the bore 16 is beveled to form a seat for the exhaust valve Ztl, the stem 211 of which passes through the sleeve 22 and is provided with a yoke 23, axle pin |24 and cam-following roller 2*,5. The sleeve 22 is fixed in the bore 16 by means of a pin 26, and the roller 2 is urged toward its cam 27 (on the drive shaft 6) by a spring 12S, the lends of which bear upon the sleeve 22 and yoke 213.

The upper periphery of the bore 17 is beveled to form a seat for the inlet lvalve vZ9 which is mounted and operated in the same manner as valve `20 but by means of a cam 3d on the drive shaft 6. `Since the air enters the chamber 11 past inlet valve 29 in a compressed state and leaves said chamber past exhaust valve Ztl in a relatively expanded state the valve 2t) is made larger than the valve 29 and the upper portion of the bore 16 is correspondingly enlarged, the bores 16 and '17 being otherwise the same.

Correspondingly, the bore `1S, connected to the upper portion of bore 16 by a lateral passage 3d, is larger than the bore 119, connected to the upper portion of the bore 17 by a lateral passage like passage 31, but not shown.

The compression chamber 2 is defined by the cylindrical wall S3, by the cylinder head 34 and by the: upper surface of the compressor piston 9. A check valve is formed in the cylinder 'head as by the provision of a centrally perforated plate 35 the opening in which is closed by a disc 36, urged toward the plate by the spring S7. The check valve permits passage of air under pressure from the chamber 2 to the compressor outlet 38.

The piston `9 is cut away at 'a plurality of points around its periphery to form, with the seal ring described below, slots 39 through which air can pass on the downward stroke of the piston, the slot walls being beveled inwardly toward the lower face of the piston as clearly shown in FIGS. f1, 2 and 3 The piston `seal ring titl` has a cylindlical part tand annular flanges 41, 42 spaced by a distance somewhat greater than the thickness of the piston periphery. On the downward inlet) stroke of the piston the upper surface ithereof moves :away `from the under surface of the flange 41, permitting passage of air around Ithe edge of ilange 42, through the beveled slots 39 and between the piston tand ilange 411 into the compression chamber 2. (FIG. l). On the upward (compression) stroke the upper surface of the piston bears firmly against the under surface of flange L11 around lthe entire periphery of the piston, enabling the ring 4t? to act as a seal while :the piston compresses the air and forces it under compression past the check valve to Ithe outlet 318 (FIG. 2). The pis-ton 9i, seal ring 410, cylinder head 34 'and plate 35 are preferably so shaped iand arranged that the volume of the chamber 2 is reduced substantially to zero at the end of the compression stroke.

The compressor outlet 3% communicates Iwith the inlet or an air-cooled heat exch-anger 43 which may be of any conventional type such as tube-and-iin, while the outlet of the heat exchanger is connected by the pipe 44 to the lower end of the bore 19. A fan 45 is mounted on the end of the drive shaft e and is enclosed in Cowling 46 arranged to enable the fan to draw ambient air through the heat exchanger 43 :and drive it past the outside of the chamber 2, which may be provided with fins 47. An air intake opening 48 is formed in the wall of the crank case portion 4 iand is preferably provided with a dust `filter 49. Said intake may merely be open to ambient air, las sho-wn, or may be connected by a suitable conduit to .the space to be cooled, for recirculation o-f the air. The lower end of the bore 1S is connected to the space to be cooled by a pipe Sil, which should be larger than the pipe 44.

In order to minimize vibration during operation it is desirable to mount counter-weights 51 on the drive shaft 6 adjacent each of th-e eccentrics 14, said counter-weights being of `a size and shape to balance kinetically the eccentrics `and the parts lassociated therewith. Shaft seals 52 are provided each side of the cam 30 in order to prevent leakageV of air under pressure in the upper part of bore 17 through said bore into the crank case. Leakage of low pressure air through bore 16 is relatively unimportant so that special steps need not be taken to prevent it.

For simplicity of maintenance it is preferable thatthe bearings should all be pre-lubricated. The piston seal ring 40` is ot a illed Teflon type, intended to run dry and having great durability.

In the cycle of operation, the air lto be cooled enters the upper cylindrical par-t of the crankcase through the intake 48, being drawn in by upward movement of the piston 9, the periphery of which is tightly sealed against the lower surface of flange 41 on seal ring 40. When .the piston 9 reaches the top of its stroke (FIG. 2) the volume of chamber 2 is nearly zero; thus, on the downward stroke, with valve 36 closed, fthe lair in the crankclase is drawn through the slots 39 into the chamber 2 until the latter attains its maximum volume-at the bottom of Lthe stroke. As the piston moves upward again the air in the chamber 2 is compressed Vand driven out past valve 36 into the compressor outlet 38, the air being at a somewhat elevated temperature corresponding to its compression, and exceeding any normal ambient temperature. The heated and compressed air ilows to and through the heat exchanger 43, Where it is cooled somewhat 'wi-thout much pressure drop, Iand thence through pipe 44 and bore 19, past valve Z9, to the expansion chamber 11. Valve 29 remains open for part of the stroke and then closes permitting expansion to take place. The closing point `is computed so that at the end of the expansion stroke the pressure in the cylinder is approximately ambient. Since the expansion chamber is formed in or carried by the compressor piston, the expansion of the air in chamber 11 is simultaneous with 'the compression of `another charge in chamber 2i, and the force of expansion, urging the piston upward, serves to recoup a substantial part (e.g., 45%) of the energy required to compress the Aair -above the piston and drive the several moving parts. As the air expands its drop in pressure is accompanied by a drop in temperature so that, at the top ott the stroke, the chamber is lled with cool air lat low pressure; the outlet valve 2* then opens, (FIG. 2) and the cooled expanded yair is driven out during the downward stroke at low pressure through bore 13 and pipe 50 to the space to be cooled. The ambient air, moved by ian 45, picks up some heat on its passage through the heat exchanger 43 but is still normally capable of having'some further cooling eiiect as it passes the tins 47 around the compression chamber 2.

As a matter of thermodynamics it might be preferable to mount the fan downstream from the compression 4 chamber' (as at the right of FIGS. l and 2), so that both the heat exchanger and the compressor would be cooled by air under suction, but the improvement in etliciency from such an arrangement is seldom sufficient to justify the increased cost of cowling and enlargement of theV over-all dimensions of the device.

While a single-cylinder unit is shown and described herein as being a practical embodiment of the invention tor effectively cooling small spaces, it will be understood that a plurality of cylinders (2, 3 or more) could be coupled axially or otherwise for more heavy duty installations. A 3 cylinder radial unit is illustrated diagrammatically in FIG. 5, each cylinder being substantially of the type described in detail herein and utilizing a common drive shaft, fan and heat exchanger, while master connecting rods 53 (corresponding to rods 15) for operating one piston are operatively coupled by links Sdi -to the other pistons.

In the modified valve arrangement of FIGS. 6 and 7 the piston `55 is provided with a central boss 56 on which is lixed a ilat circular plate y57 having a diameter larger than that ot the piston but less than that of the compression cylinder wall 33. The plate 57 is faced with a gasket 57 of a suitable plastic material and is provided twith iarcuate openings 5B `arranged in one or, preferably, several circular lines at selected radial distances from the center of the plate. The valve element in this case is a second ilat plate 59 having arcuate openings 60 so disposed radially that they are out of register with the openings 53; i.e., all openings 53 can be closed by solid parts of the plate 59 and all openings 60M will then be closed by `solid parts of the plate 57.

The plate 59 has a downwardly extending flange 61 adapted to t freely around the periphery of the plate 57 and having its vertical dimension substantially greater than the thickness of plate 57. The flange 61 is grooved near its bottom edge to receive a locking ring 62 which extends radially inward far enough to hold the plate 59 close to lthe plate 57 while permitting some relative vertical movement, comparable -to the movement permitted by the spacing of the flanges 41, 42 in iFIGS. 1, 2 and 3. The periphery of the plate 59, outside the ilange 61, is grooved to receive a piston ring 63 which seals the space between the periphery of the plate and the cylinder wall.

In operation, on the compression stroke, the plate 59 rests against the plate 57 so that all openings in both plates are closed, -as shown in full lines in FIG. 7. On the inlet stroke, as shown in broken lines in FIG. 7, the plate 57 moves down away from the plate 59, fto the extent permitted by the locking ring 62, and air passages are opened from the space between the piston head and the bottom of plate 57, through the openings 58, into the space between plates 57 and 59, through the openings 60, and into the compression chamber, as indicated by the arrows 64. It will be apparent that this arrangement, though not as simple as that shown in FIGS. 1V lto 4, provides for substantially easier passage of air into the compression chamber and so may be advantageous in some circumstances. The plate 57 is normally of metal while the plate 59 may be of aluminum to reduce its weight andthe piston ring may be ia plastic material of the Teflon type similar to that of the seal ring 40.

ln a small unit 'the drive shaft 6 may be actuated by a lexible shaft drive from the vehicle engine fan belt, but a separate combustion or electric drive may be used if desired. The source of power, being no part of the present invention, is not shown. Typical performance of a unit substantially as shown and described calls for operation at a speed of 1000 r.p.m., with 1.25 inch stroke giving a piston speed of 208 feet/min. Assuming at least volumetric efficiency the air ilow would then be approximately 34 c.f.m. On a dry air'basis, with air entering the expansion chamber at F., lthe temperature drop would be 154 with a 3 to 1 expansion ratio. Assuming 70% adiabatic eiciency, the temperature drop is 108, representing a cooling load on a 100 F. day of 65 B.t.u./rnin., or .32 ton. Moisture in the 'air will raise the outlet temperature somewhat but the cooling capacity in B.t.u.s will remain the same. IControl may be effected simply for example, by providing a manual valve (not shown) for bypassing part of the air flow around the expansion cylinder to reduce pressure at the expansion cylinder inlet.

What I claim is:

l. An air compressor comprising, `a cylinder having a head and a cylindrical Wall, a piston movable in Said cylinder and provided with an outwardly extending flange, the piston having at least one axially extending opening and an imperforate surface adjacent said opening, means for reciprocating said piston, and a movable valve element associated with said piston, the Valve element having its periphery in sealing sliding engagement with the cylindrical wall, having parts adapted to contact alternatively the upper and lower surfaces of the piston flange and being provided with at least one opening spaced from the periphery and in register axially with ran imperforate surface of the piston.

2. An lair compressor according to claim 1 in which 6 the valve element is annular and is shaped to engage said ange.

3. An air compressor according to claim l in which portions of said ange are cut away to provide slots and in which the valve element is adapted to close and open said slots.

4. A unit according to claim l in which there are a plurality of axially extending openings in the form of circumferentially spaced recesses.

5. An air compressoi according to claim l in which the outwardly extending flange is the peripheral portion of an axially slotted plate and in which the valve element is in the form of a circular plate provided with openings axially in register with imperforate areas of said slotted plate.

References Cited in the le of this patent UNITED STATES PATENTS 98,367 Forrester Dec. 28, 1869 904,459 Sergeant Nov. 17, 1908 1,927,864 Aikman Sept. 26, 1933 FOREIGN PATENTS 21,340 Great iBritain of 1894 

1. AN AIR COMPRESSOR COMPRISING, A CYLINDER HAVING A HEAD AND A CYLINDRICAL WALL, A PISTON MOVABLE IN SAID CYLINDER AND PROVIDED WITH AN OUTWARDLY EXTENDING FLANGE, THE PISTON HAVING AT LEAST ONE AXIALLY EXTENDING OPENING AND AN IMPERFORATE SURFACE ADJACENT SAID OPENING, MEANS FOR RECIPROCATING SAID PISTON, AND A MOVABLE VALVE ELEMENT ASSOCIATED WITH SAID PISTON, THE VALVE ELEMENT HAVING ITS PERIPHERY IN SEALING SLIDING ENGAGEMENT WITH THE CYLINDRICAL WALL, HAVING PARTS ADAPTED TO CONTACT ALTERNATIVELY THE UPPER AND LOWER SURFACES OF THE PISTON FLANGE AND BEING PROVIDED WITH AT LEAST ONE OPENING SPACED FROM THE PERIPHERY AND IN REGISTER AXIALLY WITH AN IMPERFORATE SURFACE OF THE PISTON. 